What New Information Is There Regarding The Potential For Society To Adapt To And Mitigate Climate Change?
Integrated Model Of The Forestry Sector Suggests That Increased Timber Growth Could Offset Carbon Emissions By 2020 An integrated modeling framework has been developed to link climate change scenarios, an ecosystem model, an economic model of the forest sector, and a carbon accounting model. Initial results indicate that elevated carbon dioxide and increasing temperature could generally increase net primary productivity and timber growth in the U.S., change land use and timber consumption by lowering prices, and could potentially offset an expected flux of carbon dioxide to the atmosphere from forest lands beginning about 2020. Changes in net ecosystem productivity under these modeled conditions are uncertain due to a lack of understanding about their effects on soil respiration.
References: (1) Forest Sector Impacts from Changes in Forest Productivity under Climate Change, Joyce, L. A., J. R. Mills, L. S. Heath, A. D. McGuire, R. W. Haynes, and R. A. Birdsey, Journal of Biogeography, in press, 1995; (2) Global Change and Forest Resources: Modeling Multiple Forest Resources and Human Interactions, Fosberg, M. A., L. A. Joyce, and R. A. Birdsey, In J. M. Reilly and M. Anderson (ed.) Economic Issues in Global Climate Change, Westview Press, Boulder, CO, pp. 235-251, 1992; (3) Past and Prospective Carbon Storage in United States Forests, Birdsey, R. A., A. J. Plantinga and L. S. Heath, Forest Ecology and Management, Vol. 58, pp. 33-39, 1993.
Elevated CO2 Found To Partially Protect Some Crops From The Effects Of Air Pollution Elevated atmospheric carbon dioxide protects at least some crops from air pollution damage. Soybean growth and yield is decreased by the air pollutant O3 and increased by elevated CO2. For example, ambient O3 reduced yield by 17% at current levels of CO2 compared to the yield in air free of O3. On the other hand, elevated CO2 (up to a doubling of current levels) increased yield up to 36%. When mixtures of the two gases were tested, it was found that CO2 enrichment partially protected soybeans from the O3 effect. However, more CO2 was required to produce a given level of protection as the O3 concentration increased. Similar results were obtained in greenhouse studies with snap beans and tomatoes. This research provides information needed to estimate the negative impact of O3, the positive impact of CO2, and the interactive effects at present and future concentrations of these gases.
References: (1) The Combined Effects of Elevated Carbon Dioxide and Ozone on Crop Systems, Miller, J. E., A. S. Heagle, S. R. Shafer and W. W. Heck, In C.V. Mathai and G. Stensland (ed.) Global Climate Change: Science, Policy, and Mitigation Strategies, Proc. Air, & Waste Management Assn. Int. Specialty Conference, 5-8 April 1994, Phoenix, AZ. VIP-40. Air & Waste Management Assn., Pittsburgh, PA. (Extended abstract), pp. 557-558, 1994; (2) Photorespiration in Soybean Treated with Elevated Carbon Dioxide and Ozone in Open-Top Chambers, Booker, F. L., S. Brunschon-Harti, C. D. Reid, E. L. Fiscus, and J. E. Miller, Plant Physiology, Submitted, 1995; (3) Vegetative Growth of Soybean as Affected by Elevated Carbon Dioxide and Ozone, Reinart, R. A., and M. C. Ho, Environment and Pollution, in press, 1995.
Elevated Atmospheric CO2 Found To Affect Ground Processes In Agro-Ecosystems Significant responses in plant root systems and their rhizospheres have been observed in CO2 enriched agro-ecosystems. Experiments in controlled environments, in open top chambers, and in free-air CO2 enrichment systems have generally shown crop growth and development to respond positively to elevated CO2. More allocation of carbon to biomass below the ground was observed. Root length and weight densities increased and overall root architecture was different. The rhizosphere of field-grown cotton growing in CO2-enriched air was altered; total soil microbial activity and saprophagous nematode populations were observed to increase. Such shifts are linked to soil carbon storage and could be important in terms of plant diseases. Soil respiration was enhanced for sorghum and soybean crops grown at elevated concentrations of CO2, probably reflecting enhanced rooting.
Ground water quality could also be affected in agro-ecosystems growing in higher levels of CO2 as more and deeper root proliferation may translate directly into more efficient uptake of water and nutrients. Response of root structure and function leads immediately to implications for changes in rhizosphere populations and activities, potential shifts in soil carbon sequestration and dynamics as well as redistribution of carbon within the soil profile, and possible effects on the soil itself. Such phenomena could well impact below ground plant competition and could certainly be important in future climates.
References: (1) Plant Responses to Atmospheric CO2 Enrichment with Emphasis on Roots and the Rhizosphere, Rogers, H.H., G.B. Runion and S. V. Krupa, Environment and Pollution, Vol. 83, pp. 155-159, 1994; (2) Elevated Atmospheric Carbon Dioxide Effects on Sorghum and Soybean Nutrient status, Reeves, D.W., H.H. Rogers, S.A. Prior, C.W. Wood and G.B. Runion, Journal of Plant Nutrition, Vol. 17, pp. 1939-1954, 1994.
Alternative Forest Management Practices Can Help Store Carbon And Slow The Rate Of Climate Change; Forest Removal Can Accelerate Greenhouse Gas Build-Up Low-cost forest management could create a sink for substantial amounts of atmospheric carbon. As much as 10% of current U.S. annual emissions could be captured (sequestered) with such low-cost measures. Increased concentrations of atmospheric CO2 will alter the carbon allocation of forests, resulting in increased carbon sequestration, particularly to the below-ground pools. Agricultural soils can also be managed to sequester carbon, as well as providing for erosion control. Conversion of natural tropical forests to farm and ranch land has the potential to increase nitrous oxide (N2O) emissions from that land by as much as a factor of three. N2O is a greenhouse gas with a global warming potential per unit mass that is 120 - 330 times greater than CO2 over the next 100 years; because much less N2O is emitted than CO2, this will be most important in cases whose CO2 emission reductions are imposed.
Reference: Reesburgh et al., in Global Atmosphere-Biosphere Chemistry, in press, 1995.
Rice Productivity To Increase With Changing Climate, Increasing Emissions Of Methane Rice is one of the world's most important grain crops. However, rice cultivation is also the second strongest anthropogenic source of methane to the atmosphere, emitting about 20% of the total. New research is underway to develop new varieties of rice and to design and demonstrate improved rice cultivation practices that reduce methane emissions. Increased concentrations of atmospheric CO2 are likely to enhance productivity of major rice varieties, providing more food, but also leading to greater emissions of methane. The associated climate changes are also predicted to substantially alter the relations between major insect pests of rice and their natural predators, potentially creating significant pest management problems. Research on new rice varieties and crop management practices are thus needed to enhance rice production without accelerating climate change.
Reference: Third Annual International Rice Research Institute (IRRI) Program Progress Report, EPA, Olszyk et al., 1995.
Establishing Shelterbelts Can Protect Crops From Climate Change A model has been produced that describes crop yield on the Great Plains as a function of the presence or absence of shelterbelts. The model indicates that shelterbelts will increase yields of several crops under scenarios of increased temperature and decreased precipitation.
Reference: Assessment of Climate Change on a Mixed Agriculture Landscape on the North American Great Plains, Brandle, J.R., et al. pp. 15-18 in National Institute for Global Environmental Change (NIGEC) annual report, University of California, Davis, 1994.
New Technologies For Mitigating Greenhouse Gas Emissions Found To Be Cost-Effective A new cleanup process for generating electrical power by fuel cells from methane emitted by landfills has been evaluated and found to be a feasible way of capturing the benefit of "clean" energy production. This process enables the conversion of methane to CO2, and, in effect, reduces the GWP of methane. Another promising technology to produce alternative transportation fuels (methanol) from biomass which appears cost-competitive with gasoline has been identified.
Reference: Landfill Gas Pretreatment for Fuel Cell Applications, Sandelli, G.J., J.C. Trocciola, and R.J. Spiegel, Journal of Power Sources, Vol. 49, pp. 143-149, 1994.
World Agriculture Can Better Adapt Than Previously Estimated If Crop Production Can Shift Agriculture is among those sectors of the economy that are most sensitive to climate change but there is also much evidence that farmers can adapt to a gradually changing climate through changes in crops and cultivars, tillage and harvesting practices, and planting schedules. While climate change like that simulated by 2xCO2 experiments of GCMs may cause crop yield losses that average 20 to 30 percent worldwide if there were no adaptation, if farmers successfully adapt to the changing climate conditions it may be possible to avoid much or all of this crop loss. Enhanced crop growth due to the direct effects of CO2 on plant growth may contribute further to offsetting crop losses or to improvements in yield. Adaptation will involve large changes in the types of crops grown in different parts of the world and the net effects will vary widely depending on the region. Adaptation may also involve abandonment of production in some areas and expansion of production into new areas. When such expansion of cropping into new areas occurs it may further disrupt natural systems that may, by then, be suffering stress from climate change. Better data on global land resources, soil quality, weather and climate, and water resources are needed to further resolve the potential for agricultural production to be maintained under multiple stresses such as climate change, tropospheric ozone, acid deposition, soil degradation, and increasing competition for scarce freshwater resources.
References: (1) World Agriculture and Climate Change: Economic Adaptations, Darwin R., M. Tsigas, J. Lewandrowski, and A. Raneses, Agricultural Economic Report Number 703, Economic Research Service, USDA, 1995; (2) Potential Implications of Climate Change for U.S. Agriculture, ERS Staff Paper, Economic Research Service, USDA, forthcoming, H.M. Kaiser, S.J. Riha, D.S. Wilkes, and R. Sampath; (3) The Impact of Global Warming on Agriculture: A Ricardian Analysis, Mendelsohn R., W.D. Nordhaus, and D. Shaw, American Economic Review, vol. 84, No. 4, (Sept., 1994). C. Stratospheric Ozone Depletion And UV Radiation